I don't have it all upstairs but who the fuck cares?

Lyric Meaning

His “upstairs” is referring to his head, or more specifically the mind. He’s saying that he’s crazy because his thoughts don’t correspond with a normal person’s.

The second part of this line, “who the fuck cares?” actually demonstrates his inability to think straight, since he’s dismissing the very fact that he’s crazy as something unimportant. Therefore he doesn’t care, but a whole lot of ducks do.